Barrier effect insulator



Aug. 16, 1966 D. w. PETERS 3,267,204

BARRIER EFFECT INSULATOR Filed Aug. 21, 1964 SAPPHHZE.

g-cALcluM CARBON/1T6 (50%) PLUS SILICON 010x105 (50%) SAPPHiRI-L /A/l/E/VTOR DAN 14 PE rE/ s United States Patent 3,267,204 BARRIER EFFECT INSULATOR Dan W. Peters, Mountain View, Calif., assignor to Stanford Research Institute, Menlo Park, Calif., a corporation of California Filed Aug. 21, 1964, Ser. No. 391,222 2 Claims. (Cl. 174-137) In high voltage measuring equipment or in equipment for measuring electrostatic voltages in which a minimum of current leakage is desired, such as electrometers, there is a need for insulators having as high a value of insulation as it is possible to obtain. It is also desirable in many applications wherein high temperatures exist to maintain the value of insulation despite the existence of high temperatures.

An object of this invention is to provide an insulator which has a higher value of insulation than that heretofore obtainable.

Yet another object of this invention is the provision of an insulator which maintains its insulating capability despite its being elevated to a high temperature.

Yet another object of the present invention is the provision of a novel and useful insulator.

These and other objects of the invention may be achieved by sintering together with a specific sintering compound made of calcium carbonate and silicon dioxide, two sapphire crystals. Electrodes may be attached to opposite surfaces of the two sapphire crystals and the value of insulation between them is the maximum obtainable.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing, which is a drawing of an embodiment of the invention.

In accordance with this invention, two sapphire crystals respectively 12, 14, which have two flat faces, are sintered together using a sintering compound. The sintering compound 16 is applied between the two opposite flat faces of the sapphire crystals 12, 14. The sapphire crystals are shown as two discs, by way of example, but not by way of limitation.

An example of a sintering compound which has been used and produces excellent results consists of a mixture of calcium carbonate and 50% silicon dioxide, which is in fine powder form and which is mixed in distilled water. A thin film of the sintering material is laid on one of the two fiat sapphire faces near the second disc and is pressed onto the first disc producing a thin boundary 16 between the two sapphire discs. The discs are then fired in air at 1750" C. for three hours, and then allowed to cool slowly. This produces a rugged bond between the two sapphire discs. If desired for supporting contacts, platinum or gold electrodes respectively 18, 20, may be airfired onto the two exposed sapphire faces, although this is not necessary. As a result of the barrier layer, carrier flow within the insulator between opposite faces is greatly inhibited.

Conductivity measurements show the multiple crystal material to have a conductivity at 800 C. which is at least six orders more than solid sapphire at the same temperature. The solid sapphire has been the best insulator available heretofore. The increased insulation effect is attributed to the barrier which is developed at the sintered layer.

There has accordingly been described and shown herein a novel, useful and improved method and means for making an insulator.

What is claimed is:

1. An insulator comprising two sapphire crystals each having a face, a sintering compound joining said two crystals at their respective faces, said sintering compound comprising a mixture of calcium carbonate and silicon dioxide.

2. An insulator as recited in claim 1 wherein said sintering compound is a mixture of 50% calcium carbonate and 50% silicon dioxide.

References Cited by the Examiner UNITED STATES PATENTS 2,548,344 4/ 1951 Buerger et al. 156-325 X 3,121,035 2/1964 Heinze 174-137 X LARAMIE E. ASKIN, Primary Examiner. 

1. AN INSULATOR COMPRISING TWO SAPPHIRE CRYSTALS EACH HAVING A FACE, A SINTERING COMPOUND JOINING SAID TWO CRYSTALS AT THEIR RESPECTIVE FACES, SAID SINTERING COMPOUND COMPRISING A MIXTURE OF CALCIUM CARBONATE AND SILICON DIOXIDE. 